What's an 11-letter word that describes a stock market crash? If you're only focused on the near term, "catastrophe" might be what comes to mind. However, for long-term investors, a better answer is "opportunity."

Major market downturns present opportunities for investors who have a long-term perspective to buy fantastic stocks at a discount. There's no way to know for sure when the next such opportunity might arise. However, whenever the next stock market crash comes, here are three great growth stocks to buy.

Red line trending down in front of a $100 bill

Image source: Getty Images.

1. Fiverr

The way people work is changing. Individuals are increasingly turning to freelancing as a primary source of income. Fiverr (FVRR 0.57%) provides a platform that connects freelancers with buyers of digital services.

Fiverr's total active buyers count stood at 2.4 million by the end of 2019. That number jumped to 3.4 million one year later. Buyers are also spending more on the platform than ever before. Unsurprisingly, Fiverr's revenue jumped 77% year over year in 2020 to $190 million. The company achieved this growth without employing a sales force.

This kind of stellar performance tends to attract competition. Microsoft reportedly is planning to launch its own freelancer service on the LinkedIn platform. The news that the tech giant could be a new rival caused Fiverr's shares to fall, but I don't think investors should be worried.

The freelancer market (estimated to total $115 billion annually in the U.S.) is large enough to support multiple players. Fiverr has also built a unique approach that eliminates many of the hassles for both freelancers and buyers. The company has a first-mover advantage and widespread support among its customer base that should enable it to continue winning over the long run.

2. Square

Square (SQ -2.54%) trades at more than 220 times expected earnings. That premium valuation could scare off many investors. But Mizuho Securities analyst Dan Dolev thinks that Square is undervalued. He believes that the fintech stock could soar 60% from its current level within the next 12 months.

It remains to be seen whether Dolev's price target will be achieved. However, the reasons behind his optimism make sense. At the top of the list is Cash App. What started out as a peer-to-peer payment app has morphed into a lot more than just that. Cash App now allows users to trade stocks and Bitcoin as well as receive paychecks and tax refunds.

Square CEO Jack Dorsey said in the company's Q4 conference call that the company plans to "double down on our commitment to Bitcoin and continue to look for new ways to connect our product lines within the Cash App." That should pave the way for even more growth.

Don't forget Square's core business serving sellers, though. With the global economy likely to recover from the COVID-19 pandemic beginning this year, that business should be set to rebound nicely. If there's a market crash, Square stock will almost certainly decline quite a bit. However, any pullback is a good time to buy Square because of its tremendous long-term prospects.

3. Teladoc Health

The surge in the use of telehealth services could be a potentially long-lasting impact of the COVID-19 pandemic. Teladoc Health (TDOC -1.65%) ranks as one of the biggest winners of this trend.

There are several companies that compete in the telehealth market, but Teladoc is the leader. Its customer base includes over 40% of the Fortune 500 and more than 50 U.S. health plans. The company's services range from acute and primary care to managing mental health.

Will demand slow down this year with the widespread availability of COVID-19 vaccines easing concerns? Nope. Teladoc projects revenue in 2021 of close to $2 billion. That's nearly double the company's revenue last year. 

Consulting firm McKinsey & Company projects that the U.S. virtual care market could approach $250 billion annually after the pandemic is over. With that kind of opportunity, Teladoc is only scratching the surface of its potential. If the stock market crashes, it's a stock that should be high on any investor's list to buy on the cheap.